Touch-screen assembly with rigid interface between cover sheet and frame

ABSTRACT

A touch-screen assembly for performing pressure sensing or force sensing is disclosed. The touch-screen assembly includes a cover sheet having touch-sensing capability and a frame having an upper surface portion. Spaced-apart adhesive islands are disposed between the cover sheet and the upper surface portion of the frame. The adhesive islands serve to secure the cover sheet to the frame and have a Young&#39;s modulus of greater than 1 MPa so that the energy associated with the touching force is not absorbed by the adhesive island. This makes for more accurate pressure-based or force-based touch sensing.

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application Ser. No. 62/003,676, filed on May 28, 2014,the content of which is relied upon and incorporated herein by referencein its entirety.

FIELD

The present disclosure relates to touch screens, and in particular to atouch-screen assembly that has a rigid interface between the cover sheetand the frame.

The entire disclosure of any publication or patent document mentionedherein is incorporated by reference.

BACKGROUND

The market for displays and other devices (e.g., keyboards) having touchfunctionality is rapidly growing. As a result, touch-sensing techniquesusing touch screens have been developed to enable displays and otherdevices to have touch functionality. Touch-sensing functionality isgaining wider use in mobile device applications, such as smart phones,e-book readers, laptop computers and tablet computers.

Touch-screen devices have been developed that rely on the amount oftouching force or pressure (force/area) applied to one or more touchlocations on the cover sheet. An accurate determination of the touchingforces associated with one or more touches is needed for thetouch-screen device to respond properly.

The conventional fabrication of a touch-screen device includes securingthe cover sheet to a support frame. This is typically accomplished withan adhesive material, such as pressure-sensitive tape, which hassubstantial pliability or compliance (i.e., a relatively low Young'smodulus). Thus, when a touching force is applied, the adhesive materialis compressed, and when the touching force is terminated, the adhesivematerial relatively slowly expands back to its original size.

For most touch-screen devices, the degree of compliance of the adhesivematerial does not substantially impact the operation of the device. Onthe other hand, for those touch-screen devices that rely on the force orpressure measurement associated with a touch event, the compression andexpansion of the adhesive material can cause an improper measurement. Inparticular, some portion of the touching force can go into compressingthe adhesive material rather than into deforming or displacing the coversheet, thereby leading to an erroneous force or pressure measurement.

SUMMARY

An aspect of the disclosure is a touch-screen assembly for performingpressure sensing or force sensing. The touch-screen assembly includes: acover sheet having an upper surface and a bottom surface, the coversheet having touch-sensing capability; a frame having an upper surfaceportion; and a plurality of islands disposed between the cover sheet andthe upper surface portion of the frame, the islands being adhesive andserving to secure the cover sheet to the frame, wherein the islands havea Young's modulus of greater than 1 MPa. The islands thus serve as arigid interface between the cover sheet and the frame.

Another aspect of the disclosure is a touch-screen assembly forperforming pressure sensing or force sensing due to at least onetouching force. The touch-screen assembly includes: a cover sheet havingan upper surface and a bottom surface, the cover sheet havingtouch-sensing capability; a frame having an upper surface portion and abase; a plurality of spaced-apart islands disposed on the upper surfaceportion of the frame, the islands having a height H and a Young'smodulus of greater than 1 MPa; and a compressible adhesive materialdisposed between the cover sheet and the upper surface portion of theframe and between the islands, the compressible adhesive materialserving to adhere the cover sheet to the frame and having anuncompressed height h≧H so that the islands limit compression of thecompressible adhesive material to a distance of h−H when the cover sheetis subjected to the at least one touching force.

Another aspect of the disclosure is a method of forming a touch-screenassembly for performing pressure sensing or force sensing due to atleast one touching force. The method includes: disposing on a surfaceportion of a frame a plurality of islands having a height H and aYoung's modulus of greater than 1 MPa; disposing a compressible adhesivematerial on the surface portion of the frame between the islands, thecompressible material having an uncompressed height h≧H; and adhering acover sheet to the frame using the compressible adhesive material, andwherein the limits limit compression of the compressible adhesive layerto a distance h−H when the at least one touching force is applied to thecover sheet.

Additional features and advantages are set forth in the DetailedDescription that follows, and in part will be readily apparent to thoseskilled in the art from the description or recognized by practicing theembodiments as described in the written description and claims hereof,as well as the appended drawings. It is to be understood that both theforegoing general description and the following Detailed Description aremerely exemplary and are intended to provide an overview or framework tounderstand the nature and character of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding, and are incorporated in and constitute a part of thisspecification. The drawings illustrate one or more embodiments, andtogether with the Detailed Description serve to explain principles andoperation of the various embodiments. As such, the disclosure willbecome more fully understood from the following Detailed Description,taken in conjunction with the accompanying Figures, in which:

FIG. 1 is an exploded view of an example touch-screen system asdisclosed herein;

FIG. 2 is a side view of the example touch-screen system of FIG. 1,wherein the cover sheet and the frame constitute a touch-screenassembly;

FIG. 3 is a plot of an applied force F_(A) (gram-force, gF) versus theresulting calculated force F_(C) (gF) for an example prior-arttouch-screen assembly wherein a compressible adhesive material in theform of a conventional pressure-sensitive adhesive (PSA) was used to fixthe cover sheet to the frame, the data of FIG. 3 being obtained by theperformance of an experiment on the prior-art touch-screen assemblywherein the applied force F_(A) was applied in the same location andrepeated about N=80 times over a fifteen-minute period;

FIG. 4 is a plot of the optical sensor response R_(OS) (arbitrary units)versus the number N of touch events conducted at an applied forceF_(A)=400 gF and is based on the data associated with FIG. 3,illustrating a variation in the optical sensor response with the numberof touch events N;

FIG. 5 is the same plot as FIG. 4 but for the touch-screen assembly asdisclosed herein that employs rigid adhesive, which substantiallyreduces the amount of relaxation that occurs after a touch event, asindicated by the substantially constant optical detector response as afunction of the number N of touch events;

FIG. 6A is a plot of the optical sensor response R_(OS) (arbitraryunits) versus the applied force F_(A) (gF) for touch-event number N=40,the plot comparing the optical sensor response for a prior-arttouch-screen assembly that uses PSA (curve PSA) and the touch-screenassembly disclosed herein that uses a perimeter of rigid epoxy (curveRE);

FIG. 6B is a plot of the optical sensor response R_(OS) (arbitraryunits) versus the applied force F_(A) (gF) comparing the optical sensorresponse of a different prior-art touch-screen assembly that uses PSA(curve PSA) to that of the touch-screen assembly disclosed herein thatuses a rigid epoxy for adhesive islands (curve RE); and

FIGS. 7A and 7B are close-up side views of an example touch-screenassembly that includes rigid stopping members with a compressibleadhesive material therebetween, wherein the rigid stopping members serveto limit the amount to which the compressible adhesive material cancompress when the cover sheet is subjected to at least one touchingforce.

DETAILED DESCRIPTION

Reference is now made in detail to various embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. Whenever possible, the same or like reference numbers andsymbols are used throughout the drawings to refer to the same or likeparts. The drawings are not necessarily to scale, and one skilled in theart will recognize where the drawings have been simplified to illustratethe key aspects of the disclosure.

The claims as set forth below are incorporated into and constitute apart of this Detailed Description.

Cartesian coordinates are shown in some of the Figures for the sake ofreference and are not intended to be limiting as to direction ororientation.

The term “rigid” when used to describe the islands discussed herein isshorthand for the resistance-to-flow of the material making up theislands when subject to pressure (i.e., being squeezed between the coversheet and the frame) due to at least one touching force applied to thecover sheet, wherein a sufficiently rigid material has a Young's modulusof greater than 1 MPa.

FIG. 1 is an exploded diagram of the main components of a touch-screensystem 10. The touch-screen system 10 includes a transparent cover sheet20, such as a rectangular sheet as shown. The cover sheet 20 includes atop surface 22, a bottom surface 24 and a perimeter or sides 26. In anexample, cover sheet 20 is configured to have at least one of capacitivetouch sensing, resistive touch sensing and optical touch sensing.Example touch screens that employ capacitive touch sensing are disclosedin U.S. Pat. Nos. 3,662,105; 3,798,370; and 7,764,274. Example touchscreens that employ resistive touch sensing are disclosed in U.S. Pat.Nos. 8,610,691 and 8,294,688. Examples of touch screens that employoptical touch sensing are disclosed in U.S. Pub. Nos. 2013/0135258 and2013/0135259.

Example materials for cover sheet 20 include any one of various types ofglass, including chemically strengthened glass such as Gorilla Glass®,available from Corning, Inc., Corning, N.Y. The cover sheet 20 can alsocomprise an acrylic, transparent polymer, etc., and can include one ormore protective coatings.

The touch-screen system 10 also includes a display device 40 thatincludes a display 42 and support electronics 44. The display device 40is configured to generate a display image (not shown) on display 42.

The touch-screen system 10 further includes a support frame (“frame”)70. The frame 70 includes walls 72 having an upper surface 74. The uppersurface 74 thus defines an upper surface portion of frame 70 and so isalso referred to as “surface portion” 74. The frame 70 also includes afloor or base 78. The walls 72 and base 78 define an open frame interior80 sized to accommodate display device 40 and any other support devices,such as wires, connectors, cabling, power supplies, circuit boards,circuitry, etc. (not shown) that are not otherwise included in supportelectronics 44. The frame 70 is shown as being rectangular by way ofexample. The frame 70 can have other shapes, as well as curved walls 72or a single curved wall that also forms base 78.

The frame 70 is shown as supporting spaced-apart islands 100 on uppersurface 74 of walls 72. In an example, islands 100 are made of anadhesive material and are used to form a relatively rigid interfacebetween cover sheet 20 and frame 70, in which case they are referred toas “adhesive islands” 100. The islands 100 have a Young's modulus ofvalues much greater than 1 MPa so that they are sufficiently rigid,i.e., they do not flow substantially or compress substantially whensubjected to pressure or when pressure is relieved, as discussed below.An example material for islands 100 is an epoxy such as a two-partepoxy. An example of a suitable two-part epoxy is MS-907 fromMiller-Stephenson Chemical Co., Inc., of Danbury, Conn. In an example,islands 100 are made of a UV-curable epoxy resin.

In an example, each island 100 can have a surface mounting area A ofbetween 0.5 mm² and 60 mm². Adjacent islands 100 have a spacing S, whichin one example is greater than 1 mm, in another example is greater than5 mm and in yet another example is greater than 10 mm. The shape ofislands 100 can vary and are shown as small squares for ease ofillustration. The islands 100 can be round, elongate, oval, etc. and canbe any reasonable shape that provides sufficient contact area on bottomsurface 24 of cover sheet 20 and upper surface 74 of walls 72 of frame70. In an example, upper surface 74 of frame 70 can be provided withindentations (not shown) that serve to at least partially containislands 100. The use of such indentations can also serve to limit anyspreading or displacement of the material making up islands 100 when atouching force F_(T) is applied to cover sheet 20.

Touch-Screen Assembly with Adhesive Islands

FIG. 2 is a side view of an example assembled touch-screen system 10wherein islands 100 are adhesive islands. The display device 40 is shownoperably arranged in frame 70 within interior 80. The cover sheet 20 isinterfaced with upper surface 74 of frame 70 and is fixed thereto viaadhesive islands 100, which are shown in black in FIG. 2 for clarity.The spacing S between adhesive islands 100 need not be uniform and canvary as a function of the position of the adhesive islands on uppersurface 74. The cover sheet 20, frame 70 and adhesive islands 100 thatfixedly interface these two components constitute a touch-screenassembly 120. FIG. 2 shows an example touching implement 150 (e.g., afinger, a stylus, a pencil, etc.) that defines a touch event TE at atouch location TL and the associated touching force F_(T). The coversheet bottom surface 24, frame upper surface 74 and adhesive islands 100define spaces or gaps 102. The adhesive islands 100 define a rigidinterface between cover sheet 20 and frame 70.

By the utilization of adhesive islands 100, cover sheet 20, whensubjected to one or more touching forces F_(T), can be displaced andotherwise allowed to flex to a degree sufficient to providetouch-sensing capability that can measure displacement, force orpressure due to touch event TE at touch location TL (or multiple touchevents TE and multiple touch locations TL). If there are too manyadhesive islands 100 and/or insufficient space S therebetween, coversheet 20 may distort (e.g., via so-called potato-chip distortion) whensubjected to one or more touching forces F_(T), and can even crack,break or shatter.

In an example, a substantial portion of cover sheet 20 at the locationwhere it is affixed to frame 70 is free to bend and otherwise move inthe Z-direction. Note also that cover sheet 20 need not be fixed toframe 70 immediately at the cover sheet perimeter 26, and the attachmentlocations can be inboard of the perimeter. The use of islands 100 servesto define a rigid interface between cover sheet 20 and frame 70.

FIG. 3 is a plot of an applied force F_(A) (gram-force, gF) versus thecalculated force F_(C) (gF) for an example prior-art touch-screenassembly wherein a compressible adhesive material in the form of apressure-sensitive adhesive (PSA) was used to fix cover sheet 20 toframe 70. The data of FIG. 3 were obtained by the performance of anexperiment on the prior-art touch-screen assembly wherein an appliedforce F_(A) was applied in the same location and repeated about N=80times over a fifteen-minute period. The number N is thus the number oftouch event TE.

The applied force F_(A) for the repetitive touch events TE was changedfrom 0 to 850 gF and the response measured. The measured response tookthe form of a measured displacement of cover sheet 20 using an opticalproximity sensor. The measured displacement was then converted into acalculated resulting force F_(C) using a lookup table assembled earlierbased on empirical data.

The plot of FIG. 3 shows six different curves corresponding to the touchevent numbers N=1, N=2, N=5, N=10, N=40 and N=80 for the given appliedforce F_(A). FIG. 3 clearly shows that the force readings change,depending on the number of presses or touches. This is due to therelaxation of the prior-art PSA and the variation in the amount ofcompression and relaxation of the PSA that occurs over time.

FIG. 4 is a plot of the optical sensor response R_(OS) (arbitrary units)versus press number P# for an applied force F_(A)=400 gF. The data ofFIG. 4 shows how the optical sensor response changes with the touchevent number N due to the variation in the compression and of the PSAover time.

FIG. 5 is the same plot as FIG. 4 but for a modified version of thetouch-screen assembly 120 as disclosed herein that employs a perimeterof rigid adhesive. The perimeter of rigid adhesive did not compress orrelax over time when subjected to pressure (e.g., the compressive forceformed by touching force F_(T)). This resulted in consistentdisplacement readings from the optical sensor, which translated into aconsistent displacement of cover sheet 20.

FIG. 6A is a plot of the optical sensor response R_(OS) (arbitraryunits) versus the applied force F_(A) (gF) for touch-event number 40,wherein the plot compares the optical sensor response for a prior-arttouch-screen assembly that uses PSA (curve PSA) to that of atouch-screen assembly that uses a perimeter of rigid epoxy (curve RE).The measurements for the prior-art configuration for the touch-screenassembly are shown as the solid line, while the measurements for thetouch-screen assembly using a perimeter of rigid epoxy are shown as thedashed line labeled RE.

The data of FIG. 6A show an overall reduced optical sensor responseR_(OS) for the perimeter of epoxy versus the PSA. However, usingadhesive islands 100 rather than a continuous perimeter and adjustingthe spacing S and the surface mounting area A of the adhesive islandsallows for tailoring the amount of displacement and freedom of movementof cover sheet 20 and thus the magnitude of the optical sensor responsefor a given touching force F_(T).

FIG. 6B is a plot of the optical sensor response R_(OS) (arbitraryunits) versus the applied force F_(A) (gF) comparing the optical sensorresponse for a prior-art touch-screen assembly that uses PSA (curve PSA)to that of a touch-screen assembly that uses a rigid epoxy for adhesiveislands (curve RE). The measurements for the prior-art configuration fortouch-screen assembly 120 are shown in the curve labeled PSA, while themeasurements for the touch-screen assembly that employs adhesive islands100 of rigid epoxy are shown as the curve labeled RE. The data of FIG.6B show an overall increase in the optical sensor response R_(OS) foradhesive islands 100 of rigid epoxy versus the PSA. Measurements of thetouch sensitivity of touch-screen assembly 120 show similar overallsensitivity to prior-art configurations of the touch-screen assembly,but without the attendant errors in the measurement of the amount oftouching force F_(T).

Touch-Screen Assembly where Islands Serve as Stopping Members

FIG. 7A is a close-up side view of a portion of touch-screen assembly120 illustrating an example embodiment wherein a relatively flexible(i.e., non-rigid) adhesive material 200, such as conventional PSA,resides in spaces or gaps 102 between spaced-apart islands 100. In anexample, islands 100 have a height H that is equal to or less than theinitial (uncompressed) height h of adhesive material 200.

In the configuration where H<h, islands 100 are not adhered to coversheet 20 at bottom surface 24 and so do not serve to bond the coversheet to frame 70. Instead, there is a small gap of size h−H, withislands 100 serving as rigid stopping members that act as a hard stop tothe compression of adhesive material 200 when cover sheet 20 issubjected to a touching force F_(T), such as is shown in FIG. 7B. InFIG. 7B, adhesive material 200 is slightly compressed due to touchingforce F_(T) from implement 150 until h=H. At that point, islands 100contact bottom surface 24 of cover sheet 20 and serve as stand-offs,thereby preventing further displacement of the cover sheet andpreventing further compression of adhesive material 200. The islands 100define a rigid interface between cover sheet 20 and frame 70 when h=H.

In this manner, conventional compliant adhesive material 200 can be usedto interface cover sheet 20 with frame 70 without the adversecompression and relaxation effects that lead to erroneous measurementsof the displacement of the cover sheet and/or the touching force F_(T).Further, since islands 100 are not performing an adhesive function inthis embodiment, they can be more spaced apart than usual, therebyproviding greater latitude for cover sheet 20 to be displaced andotherwise flexed when one or more touching forces F_(T) are applied.

In an example, islands 100 are made of any material having a Young'smodulus of greater than 1 MPa and that can be fixed to upper surfaceportion 74 of frame 70. In various example applications, it may beeasiest to form islands 100 from an adhesive material, such as an epoxy.The use of rigid islands 100 in the present embodiment serves to definea rigid interface between cover sheet 20 and frame 70 while stillallowing for the use of non-rigid adhesive material to secure the coversheet to the frame.

It will be apparent to those skilled in the art that variousmodifications to the preferred embodiments of the disclosure asdescribed herein can be made without departing from the spirit or scopeof the disclosure as defined in the appended claims. Thus, thedisclosure covers the modifications and variations provided they comewithin the scope of the appended claims and the equivalents thereto.

What is claimed is:
 1. A touch-screen assembly for performing pressuresensing or force sensing, comprising: a cover sheet having an uppersurface and a bottom surface, the cover sheet having touch-sensingcapability; a frame having an upper surface portion; and a plurality ofislands disposed between the cover sheet and the upper surface portionof the frame, the islands being adhesive and serving to secure the coversheet to the frame, wherein the islands have a Young's modulus ofgreater than 1 MPa.
 2. The touch-screen assembly according to claim 1,wherein the cover sheet operably supports at least one of capacitivetouch-sensing, resistive touch-sensing and optical touch-sensing.
 3. Thetouch-screen assembly according to claim 1, wherein the adhesive islandsare equally spaced apart.
 4. The touch-screen assembly according toclaim 1, wherein the islands are formed from epoxy.
 5. The touch-screenassembly according to claim 4, wherein the islands are formed from aUV-curable epoxy resin.
 6. The touch-screen assembly according to claim1, wherein the islands have a surface mounting area of between 0.5 mm²and 60 mm².
 7. The touch-screen assembly according to claim 6, whereinadjacent islands define a spacing that is greater than 1 mm.
 8. Thetouch-screen assembly according to claim 6, wherein the frame includes aplurality of walls that each has an upper surface, and where the uppersurfaces define the upper surface portion of the frame.
 9. Thetouch-screen assembly according to claim 1, wherein the cover sheetcomprises a chemically strengthened glass.
 10. A touch-screen assemblyfor performing pressure sensing or force sensing due to at least onetouching force, comprising: a cover sheet having an upper surface and abottom surface, the cover sheet having touch-sensing capability; a framehaving an upper surface portion and a base; a plurality of spaced-apartislands disposed on the upper surface portion of the frame, the islandshaving a height H and a Young's modulus of greater than 1 MPa; and acompressible adhesive material disposed between the cover sheet and theupper surface portion of the frame and between the islands, thecompressible adhesive material serving to adhere the cover sheet to theframe and having an uncompressed height h≧H so that the islands limitcompression of the compressible adhesive material to a distance of h−Hwhen the cover sheet is subjected to the at least one touching force.11. The touch-screen assembly according to claim 10, wherein the islandscomprise an epoxy.
 12. The touch-screen assembly according to claim 10,wherein the adhesive material comprises a pressure-sensitive adhesive.13. The touch-screen assembly according to claim 10, wherein the coversheet comprises a chemically strengthened glass.
 14. The touch-screenassembly according to claim 10, wherein the touch-sensing capability ofthe cover sheet is based on at least one of capacitive sensing,resistive sensing and optical sensing.
 15. A method of forming atouch-screen assembly for performing pressure sensing or force sensingdue to at least one touching force, comprising: disposing on a surfaceportion of a frame a plurality of spaced-apart adhesive islands;adhering a cover sheet to the frame using the spaced-apart adhesiveislands; and allowing the spaced-part adhesive islands to become rigidto have a Young's modulus of greater than 1 MPa.
 16. The methodaccording to claim 15, wherein the space-apart adhesive islands comprisean epoxy.
 17. The method according to claim 16, wherein the cover sheetcomprises a chemically strengthened glass.
 18. A method of forming atouch-screen assembly for performing pressure sensing or force sensingdue to at least one touching force, comprising: disposing on a surfaceportion of a frame a plurality of islands having a height H and aYoung's modulus of greater than 1 MPa; disposing a compressible adhesivematerial on the surface portion of the frame between the islands, thecompressible material having an uncompressed height h≧H; and adhering acover sheet to the frame using the compressible adhesive material, andwherein the plurality of islands limit the compression of thecompressible adhesive layer to a distance h−H when the at least onetouching force is applied to the cover sheet.
 19. The method accordingto claim 18, further including forming the islands from an epoxy. 20.The method according to claim 19, wherein the compressible adhesivematerial comprises a pressure-sensitive adhesive.